When shooting a cine film, it is conventional practice to record in the marginal part of the film, between the successive perforations in the case of a 16 mm film, or outside these perforations in the case of a 35 mm film, coded information which corresponds to the conditions in which the corresponding filmed sequences were shot. Such information may be relative, for example, to the time of shot-taking, to the camera used, to the diaphragm employed, to the lens used, etc.
The information concerning the time is used in particular for ensuring, during projection of the cine film, synchronization of the advance of this film with that of a sound recording support on which the sound corresponding to the different shot-taking sequences was recorded, independently, during shooting.
In the process of recording coded information described in U.S. Pat. No. 4,659,198, every information associated with an image is recorded in the form of a matrix assembly of dots or "optical bits" which are recorded on the marginal part of the film, distributed in a matrix comprising for example seven longitudinal columns and thirteen transverse rows. To ensure subsequent synchronization, it is also provided, in this process, to record, before each matrix of dots or "optical bits" corresponding to a group of coded information, a transverse framing pattern constituted by a single combination of dots which is different from all the combinations corresponding to the different information characters, then, during recording of the different successive characters constituting the same group of coded information, a longitudinal framing pattern, along a longitudinal for bordering the matrix, this longitudinal framing pattern being constituted by an alternation, along said row, of dots and absences of dot aligned respectively with the various columns of the matrix in which successive characters are recorded.
With such a system of recording coded information on a cine film, it is necessary, when this film is being projected, to use a device for reading the dots or "optical bits" in order to ensure synchronization of the film with the sound recording support such as a magnetic tape or a compact disc. Such synchronization is permanently ensured by comparing the coded information associated with each image and defining an "address" relative to this image, with a corresponding "address" on the sound recording support. This support, servo-controlled by the advance of the film, may also bear in coded form the contents of sub-titles or other events which it is desired to show around or within the screen during projection of the images. In this way, several sound versions, in different languages, and corresponding sub-titles may be associated with a film. Consequently, if original images of the film are absent, due to a cut of this film and subsequent connection thereof, this absence of image is immediately detected and the servo-control device automatically accelerates the sound recording support in order to make up the delay and ensure that the sound emission from the loudspeaker corresponds strictly to the images projected.
A system of projection therefore requires the provision of a reader of the dots or "optical bits" present on the film, which is relatively precise. As the dots or "optical bits" are of very small dimensions, this reader must be very precise and it is generally constituted by a relatively complex assembly comprising, on one side of the film, a lamp and a condenser and, on the other side of the film, a lens to form a clear image of the dots of the coded information or "addresses" on a detector which may for example be of the CCD type.
Furthermore, such a system of projection, with servo-control of the sound recording support by the cine film by comparison of addresses, supposes that all the information coded on the film is read entirely and with precision. Now, cine films are rapidly scratched, after several projections, and these longitudinal scratches may lead to a defective identification of the longitudinal framing pattern, if the scratch is produced in the zone of this pattern, or to a loss of certain coded information.
It is an object of the present invention to overcome these drawbacks by providing a process which makes it possible, during projection of the film, both considerably to facilitate reading of the dots or "optical bits" constituting the coded information and to ensure in reliable manner servo-control between the cine film and the sound recording support, even if that zone of the film bearing the coded information presents scratches.